High impact information on HOP2

• The hop2 mutant arrests at the pachytene stage of meiotic prophase with the RecA-like protein Dmc1 located at numerous sites along synapsed chromosomes [1].
• The meiosis-specific Hop2 protein localizes to chromosomes prior to and during synapsis and in the absence of the double-strand breaks that initiate recombination. hop2 strains sustain a wild-type level of meiotic double-strand breaks, but these breaks remain unrepaired [1].
• We propose that the Hop2 protein functions to prevent synapsis between nonhomologous chromosomes [1].
• The hop2 mutant of S. cerevisiae displays a novel phenotype: meiotic chromosomes form nearly wild-type amounts of synaptonemal complex, but most chromosomes are engaged in synapsis with nonhomologous partners [1].
• Interestingly, noncrossover recombination is absent, indicating a role for Mnd1/Hop2 in the designation of DSBs for noncrossover recombination [2].

Biological context of HOP2

• Our results support a model in which Mnd1/Hop2 is required for DNA-DNA interactions that help ensure Dmc1-mediated stable strand invasion between homologous chromosomes, thereby preserving genomic integrity [2].
• Mnd1/Hop2 facilitates Dmc1-dependent interhomolog crossover formation in meiosis of budding yeast [2].
• The HOP2 gene is expressed specifically in meiotic cells, with the transcript reaching maximum abundance early in meiotic prophase [3].
• The Saccharomyces cerevisiae HOP2 gene is required to prevent formation of synaptonemal complex between nonhomologous chromosomes during meiosis [3].

Physical interactions of HOP2

• In Saccharomyces cerevisiae, the Hop2 protein forms a complex with the Mnd1 protein and is required for the alignment of homologous chromosomes during meiosis, probably through extensive homology matching between them [4].

Other interactions of HOP2

• Biochemical studies indicate that Hop2 and Mnd1 proteins form a stable heterodimer with a higher affinity for double-stranded than single-stranded DNA, and that this heterodimer stimulates the strand assimilation activity of Dmc1 in vitro [5].
• We conclude that Rad51 is capable of carrying out a homology search independently, whereas Dmc1 requires additional factors such as Hop2 [6].
• HOP2 pre-mRNA is spliced efficiently in the absence of the Mer1 and Nam8 proteins, which are required for splicing the transcripts of two other meiosis-specific genes [3].

References